1. Field of Invention
The invention relates to a continuous measurement process for the surface roughness of a cold-rolled product, more particularly cold-rolled strip.
2. Description of Prior Art
The roughness of cold-rolled strip has, of course, a considerable effect on its cold-working properties and its appearance after painting. Cold-rolled strip should therefore have a surface roughness which is as constant as possible throughout; also, strips to be used for the same purpose should all be of comparable roughness. It is therefore important to monitor the roughness of strip produced in a cold-rolling mill to ensure very rapid detection of any deviation from permitted values.
Conventional monitoring takes the form of periodic sampling and laboratory testing of a strip sample. This method has the disadvantage of being discontinuous and of requiring rolling to stop for the sample to be taken by cutting the strip. Also, this kind of examination cannot help to determine the state of the entire strip. Furthermore, since the sample is taken in the inoperative state, since the strip has to be stopped, it is not always representative of the roughness produced in the operative state.
Of the possible methods of continuously determining the roughness of the surface of a rolled product such as cold-rolled strip, only the optical method is at present used. In the optical method a beam of visible light is transmitted on to the surface at a predetermined angle of incidence to the normal to the surface at the position of beam incidence, the beam reflected by the surfaces is collected, the reflected light energy is measured, and a measurement of surface roughness is deduced.